Sleep can be broken up into two basic types: REM (rapid eye movement) sleep, and non-REM sleep, which is further broken up into three separate stages. Both are associated with specific brain wave activity, and serve different functions for the brain and the body.
When you have a good night’s rest, you’ll make your way through all stages several times, with REM periods taking up longer, deeper periods the closer you get to waking. Understanding the different sleep stages can make you more aware of the quality of sleep you’re getting, and why maybe those 8 hours of occasionally interrupted sleep weren’t as restful as less, but deeper and more restful, sleeps. So, here goes:
The first part of non-REM sleep is the switch from being conscious to sleeping. During this short time that lasts only a few minutes, your heartbeat, breathing, and eye movements slow down, and your muscles begin to relax. You usually will twitch and move around a bit still. While this is all happening in a fairly light sleep state, your brain waves start to slow down from their awake patterns.
The second phase of non-REM sleep is another stage of lighter sleep that leads into deep. Your heartbeat and breathing slow quite a bit more and your body relaxes further. Your eyes stop moving and your body temperature lowers, while brain waves continue to slow with intermittent bursts of electrical activity. Stage 2 is where you spend more of your sleep cycles than any other stages of your snooze.
The last phase of non-REM sleep is where you finally reach that deeper, more restorative level of sleeping that helps you wake up refreshed in the a.m. You get longer periods of it during the first half of the night, and your heartbeat and breathing will be slowed to their lowest levels during this period. Your muscles are also extremely relaxed and brain waves are at their slowest. During this stage of sleep, folks are often difficult to awaken.
Then you finally make it to REM sleep, the first cycle of which you get to about 90 minutes after nodding off. Your eyes move rapidly from side to side (while staying closed, thank goodness). This is where the term “rapid eye movement” came from. Brain wave activity is mixed, similar to that of when you are awake. Breathing is fast and irregular, and heart rate rises close to waking levels. This is when most dreaming occurs, as your brain is busy creating all kinds of scenarios in your head. Arm and leg muscles will normally become paralysed, which will hold you back from acting out what you are imagining. Interestingly, the older you get, the less time you spend in REM sleep.
To that we want to say: no matter your age, never stop dreaming.